Coding Version 0 and Challenges Faced

Kickstarting coding

The very first step in developing the Matrix bridge for qaul was to attempt and create a login functionality into the matrix from the qaul code. As mentioned earlier, By reffering the examples/ in matrix-sdk which was latest at 0.6.2 by the time I am writing this, I wrote a new file inside qaul-matrix-bridge binary called relay_bot.rs along with a connect() method which will allow us to connect with matrix.

Dependencies conflicts

With the new connect() method and the relay_bot.rs code, compiler complaint heavily with list of errors. On debugging, The errors were about dependency version conflict.

With latest matrix-sdk 0.6.2, Version mismatched for libp2p which at the time has latest 0.51.x and qaul was using 0.50.0 and 0.52.0 was about to release officially within next upcoming month. The code was compiling if we downgrade matrix-sdk to 0.4.0. But then we lose some methods which connects qaul directly with some abstraction level to matrix.

I reported this to MathJud. He took some time to look at the dependency tree and figured out the exact conflicts. We were using libp2p at 0.50.x and it had libp2p-swarm-derive. Now the matrix-sdk and libp2p-swarm-derive has two packages in common

quote
syn

And the syn package had a big version number change 1->2. But If libp2p 0.52.0 gets released, It would have solved the conflict but it would require us to do some code changes to upgrade qaul to onboard 0.52.0 of libp2p. So, For inital rounds of test, We decided to stick with an older version of matrix-sdk with no change inside qaul.

I have although asked the maintainers of libp2p about when they'd plan their next release in one of their open issues : Link to discussion on lib p2p 0.52.0 release

Sailing the Boat

I have now started coding with matrix-sdk 0.4.0 and implemented the very first feature which listens on the room for any messages on matrix and return us back with a simple message.

The relay_bot::connect() method were rightly used for login into matrix and listening on the matrix client for any activity or interact with it. Since this process required synchronus listening on the matrix service, It actually blocked the qaul-cli. We needed to run both the process simultaneously and synchronously.

Keep checking for messages on matrix
Keep checking for messages in qaul

To make both the calls on both side sync, We thought to run the process of matrix login and configuration inside a different thread. This way, the process kept running in new thread without blocking our qaul-cli. Another option was that we may have polled the matrix part inside the loop which runs in qaul for every 10 miliseconds for checking any command line events or RPC events. But, It comes with a problem of overhead since, relay_bot::connect() logs in every time we run in a loop and tweaking it was not likely the best option. Running in separate thread was the best thing which we got to see clearly.


#![allow(unused)]
fn main() {
thread::spawn(|| {
        // connect the matrix bot with the qaul-cli
        match relay_bot::connect() {
            Ok(_) => {
                println!("Matrix-Bridge connecting");
            }
            Err(error) => {
                println!("{}", error);
            }
        }
    });
}

Next I have worked on developing the !qaul command and !users-list command which will listen to messages from matrix and respond from qaul with appropriate message.

Now that we know the using a !qaul command we are able to trigger a message from qaul broadcast, This ensures the in qaul we are able to listen successfully for all the messages comming from matrix room.

This is actually a simple implementation given by matrix-sdk itself. Here is the snippet below.

We first login to our bot client using the configuration which we have had in our matrix running thread. Then on that configuration, We listen for any incomming messages every few miliseconds (200ms for testing but should be less when it gets in real implementation).


#![allow(unused)]
fn main() {
let client = Client::new_with_config(homeserver_url, client_config).unwrap();
    client
        .login(&username, &password, None, Some("command bot"))
        .await?;
    println!("logged in as {}", username);

    // An initial sync to set up state and so our bot doesn't respond to old
    // messages.
    client.sync_once(SyncSettings::default()).await.unwrap();

    // Listening for all the incomming messages on bot account.
    client.register_event_handler(on_room_message).await;
}

and the magical implementation if any message is received is done in this function on_room_message.


#![allow(unused)]
fn main() {
async fn on_room_message(event: SyncMessageEvent<MessageEventContent>, room: Room) {
    // If the room that receives the message is joined by the bot account.
    if let Room::Joined(room) = room {
        // Extract out the message content and name of sender.
        let (msg_body, msg_sender) = if let SyncMessageEvent {
            content:
                MessageEventContent {
                    msgtype: MessageType::Text(TextMessageEventContent { body: msg_body, .. }),
                    ..
                },
            sender: msg_sender,
            ..
        } = event
        {
            (msg_body, msg_sender)
        } else {
            return;
        };
        // If bot is replying then the same message in matrix room is considered as received and we 
        // get double copy of the sent message in qaul. So we don't listen for the messages where 
        // sender is qaul-bot.
        if msg_sender != "@qaul-bot:matrix.org" {
            let msg_text = format!("{} : {}", msg_sender, msg_body);

            // on receiving !qaul in matrix, Send message
            if msg_body.contains("!qaul") {
                let content = AnyMessageEventContent::RoomMessage(MessageEventContent::text_plain(
                    "I am a message sent from qaul network\n",
                ));
                room.send(content, None).await.unwrap();
            }

            // on receiving !users-list in matrix, Send it to command line
            if msg_body.contains("!users-list") {
                let input_line = "users list".to_string();
                let evt = Some(EventType::Cli(input_line));
                if let Some(event) = evt {
                    match event {
                        EventType::Cli(line) => {
                            Cli::process_command(line);
                        }
                    }
                }
            }
        } else {
            println!("Sent the message in the matrix room by !qaul-bot");
        }
    }
}
}

Writing a Matrix Bridge in Rust

Coding Version 0 and Challenges Faced

Kickstarting coding

Dependencies conflicts

Sailing the Boat